This invention relates to a foldable case blank provided with framed portions at the peripheral edges of an upper surface of a case when the case blank is fabricated by a case making machine.
FIG. 1 shows a conventional foldable case blank A1. Terms used hereinafter for designating portions of the case blank A1 are those of the respective positions constituting a case when the case blank is fabricated as a case. In FIG. 1, an upper plate or board 1, a bottom plate 2, and front and rear plates 3 and 4 are connected in series through longitudinal foldable lines 5, 6 and 7 so that these plates face respectively when the case blank A1 is folded along the foldable lines 5, 6 and 7 to form a substantially rectangular parallelepiped case. A connecting piece 8 is further connected to the upper edge, as seen in FIG. 1, of the front plate 3 through a longitudinal foldable line 9, and connecting pieces 10 through 17 are also connected to both sides of the upper, bottom, front and rear plates 1, 2, 3 and 4 through transverse foldable lines 18 through 25 for forming side plates when the case blank A1 is fabricated as a case, to close both longitudinal side openings of the case. The side plate pieces 10, 11, 14 and 15 connected to both side edges of the upper and bottom plates 1 and 2 have substantially the same configuration, and the side plate pieces 12, 13, 16 and 17 connected to the front and rear plates 3 and 4 have also substantially the same configuration, respectively. Furthermore, connecting pieces 27, 28, 29 and 30 are connected to the side plate pieces 10, 11, 14 and 15 at the corner portions thereof on the sides near the side plate pieces 12, 13, 6 and 17, respectively. These connecting pieces 27, 28, 29 and 30 are constructed to be foldable along foldable lines 31, 32, 33 and 34 which extend at angles of 45.degree. with respect to the foldable lines 18, 19, 22 and 23, respectively, and these connecting pieces 27, 28, 29 and 30 are bonded to the corresponding side plate constituting pieces 12, 13, 16 and 17 when the case blank A1 is fabricated. On the central portion of the upper plate 1 is a take-out hole 26 through which an article can be taken out when the case is made.
The case blank A1 can be automatically folded by using an automatic case making machine, not shown, of the type generally used in the manner described hereinbelow.
The case blank A1 is at first folded along the foldable lines 5, 6, 7 and 9, 18 through 25, and 31 through 34, and paste is then applied to the connecting pieces 27 through 30 and 8 to be bonded to the outer surfaces of the side plate pieces 12, 13, 16 and 17, and the connecting piece 8, and to the inner surfaces of the connecting pieces 27, 28, 29 and 30 as well as the end portion of the inner surface of the bottom plate 2, thus obtaining a folded case A2 such as shown in FIG. 2.
When the folded case A2 is actually fabricated, the folded case A2 has forces applied in the directions shown by solid arrows in FIGS. 2 and 3, i.e. along the diagonal edges 5 and 7, thus fabricating a rectangular parallelepiped case A3 as shown in FIG. 3.
With the case A3 thus fabricated, the case A3 is provided with pressure resisting characteristics sufficient to resist against the force or pressure from the solid-arrowed directions on the foldable lines 5 and 7, but insufficient to resist the force or pressure from the dot-arrowed directions acting on the diagonal lines 6 and 9. In a certain case, the side plate constituting pieces 10 through 17 may be folded inwardly of the case A3 along the foldable lines 31 through 34 by a relatively weak force or pressure applied thereon.
Accordingly, in a case, for example, where fruit is accommodated in the case A3, if any force is applied from the direction of the line 6 or a plurality of such cases are stacked, the cases may be deformed thereby damaging the fruit. Furthermore, in a case where a plurality of cases A3 are stacked, the cases A3 may be extremely deformed and shifted with each other or has adversely fall down.